Air-cooled single-cylinder internal combustion engine

ABSTRACT

An air-cooled single-cylinder internal combustion engine comprising a flywheel blower and a mounting plate attached to the engine at the blower end, to one side of which a sheet-metal shell encompassing the engine is attached which defines a first cooling-air duct in combination with the crankcase and a second cooling-air duct in combination with the cylinder, and to the other side of which a cowl covering the flywheel blower with the cooling-air spiral and interconnecting the two cooling-air ducts via perforations of the mounting-plate is attached.

United States Patent Freyn AIR-COOLED SINGLE-CYLINDER INTERNAL COMBUSTION ENGINE Inventor: Fritz Freyn, Graz, Austria Assignee: Hans List, Graz, Austria Filed: Feb. 22, 1974 Appl. No.: 444,900

Foreign Application Priority Data Mar. 6, 1973 Austria 1985/73 US. Cl. 123/41.31; 123/41.7; 123/41.72; 123/41.86; 123/196 AB Int. Cl. FOlP l/06 Field of Search 123/41.3l, 41.86, 196 AB, l23/4l.7, 41.72, 41.62

References Cited UNITED STATES PATENTS 9/1970 Freyn l23/41.3l

6/1972 Hatz 123/4l.31

12/1940 Jacobi l23/4l.3l

Oct. 14, 1975 FOREIGN PATENTS OR APPLICATIONS 885,152 12/1961 United Kingdom 123/4l.31

Primary ExaminerCharles J. Myhre Assistant Examiner-Daniel J. OConnor Attorney, Agent, or Firm-Watson, Cole, Grindle & Watson [57] ABSTRACT An air-cooled single-cylinder internal combustion engine comprising a flywheel blower and a mounting plate attached to the engine at the blower end, to one side of which a sheet-metal shell encompassing the engine is attached which defines a first cooling-air duct in combination with the crankcase and a second cooling-air duct in combination with the cylinder, and to the other side of which a cow] covering the flywheel blower with the cooling-air spiral and interconnecting the two cooling-air ducts via perforations of the mounting-plate is attached.

4 Claims, 4 Drawing Figures AIR-COOLED SINGLE-CYLINDER INTERNAL COMBUSTION ENGINE The invention relates to an air-cooled single-cylinder internal combustion engine comprising a flywheel blower and a cooling-air duct emerging from the delivery end of the blower and leading to the cylinder and cylinder head.

In air-cooled single-cylinder internal combustion engines the cooling-air blower is generally designed as a flywheel blower for the sake of simplicity, the blower impeller being located at the outside of the flywheel so as to admit the cooling-air to the blower through an aperture at the front end of the flywheel housing. However, this design largely fails to meet various requirements regarding the cooling, and in particular to solve the problem of adequately cooling the engine oil.

It is the object of the invention to produce a cooling system for air-cooled single-cylinder internal combustion engines of the type hereabove described in a simple manner, said system including also the cooling of the engine oil and distinguishing itself by simple assembling conditions and possible weight savings. According to the invention, the blower is attached to the side of the flywheel facing the engine and a mounting plate extending in transverse relation to the crankshaft axis and preferably consisting of a sheet metal is provided between the engine and the blower. Said mounting plate carries a cowl covering the flywheel with the blower and cooling-air spiral at the blower end and a sheet-metal shell encompassing the engine at the engine end, said shell forming in addition to a guide means leading to the cylinder and cylinder head also an additional guide means separated from the former by means of a partition and extending alongside the crankcase in the direction of the suction end of the blower, each of the cooling-air guide means being connected to the chamber including the flywheel blower and covered by means of the cow] via a perforation of the mounting plate.

By this arrangement it is possible to use the coolingair prior to its entry into the casing for the cooling of almost the entire outer surface of the crankcase, thereby decisively lowering the temperature of the engine oil. At the same time, it is possible, by appropriately dimensioning the cross-sections of the cooling-air duct provided between the sheet-metal shell and the crankcase, to distribute the velocity of cooling-air currents in such a manner as to take differing cooling re: quirements of the various areas of the crankcase duly into account. I

Another particular advantage is derived from a considerable reduction of weight resulting from the substitution of a plain cowl, preferably also made from sheetmetal, for the flywheel housing normally made from a casting. In addition, the assemblage is facilitated by the fact that of all the elements constituting the cooling-air ducts, only the mounting plate is to be attached to the engine. Finally, by an appropriate exchange of the sheet-metal members forming the cooling-air ducts of the same basic engine, variations in engine design are feasible without altering the basic engine.

A further advantage of the design according to the invention resides in the fact that in spite of substantially improved cooling conditions which are particularly important in connection with high-powered engines of recent design, the external dimensions of the engine provided with the cooling-air ducts are only slightly increased comparatively, said increase being restricted to the crankcase area.

According to another feature of the invention the mounting plate is attached in spaced relation to the engine by means of bosses with bolts protruding from the crankcase and/or the cylinder head. Thus the necessary machining for the connection of the mounting plate is restricted to the provision of tapholes on the bosses and of bores in the mounting plate in alignment therewith. Furthermore, the provision of a gap between the crankcase and the mounting plate assures unimpeded access for the cooling-air directed alongside the crankcase walls to the entire periphery of the blower impeller.

According to yet another particularly advantageous embodiment of the invention, the partition in the internal combustion engine separating the two cooling-air ducts presents a perforation adapted to the periphery of the cylinder and is located in spaced relation to and above the upper boundary surface of the crankcase, encompassing the cylinder. As a result, additional free flow cross-sections associated with the cooling-air duct leading to the suction end of the blower remain between the upper boundary surface of the crankcase and the partition located above.

Further details of the invention will be explained hereafter with reference to the accompanying drawing wherein FIG. 1 shows a side elevation of an air-cooled singlecylinder internal combustion engine of conventional design,

FIG. 2 a front view of the known engine according to FIG. 1.

FIG. 3 shows a side elevation of an internal combustion engine according to the invention, and 7 FIG. 4 a front view of the engine according to FIG. 3.

In all figures the walls serving for the conduct of air are shown in sectional views and identical reference numbers are used for similar members.

the air-cooled single-cylinder internal combustion engine of known design 1 shown in FIGS. 1 and 2 comprises a flywheel housing consisting of a blower impeller 3 attached to the outside of the flywheel 2 and rotating at the same speed as the latter, and located within the flywheel housing 4 forming also the spiral housing of the blower. The flywheel housing 4 is provided with an aperture 6 in concentric relation to the crankshaft 5 of the engine 1 for the supply of the cooling-air to the blower impeller 3. Arranged around the cylinder 8 and cylinder head 9 mounted on the crankcase 7 is an airduct housing 10 of an approximately U-shaped crosssection forming in combination with the cylinder cooling surfaces a cooling-air duct 11 for the air delivered by the blower 3.

As appears from the drawing, the cooling of engines of conventional design is limited to the immediate area of the cylinder and of the cylinder head 9, whereas the crankcase 7 is not affected by the blower cooling. Heat can be exchanged between the crankcase 7 and its environment only by means of radiation and convective heat exchange with the undisturbed ambient air. This natural exchange of heat is in many cases, particularly with high-powered high-speed engines, inadequate for the maintenance of a sufficiently low engine oil temperature.

This drawback is remedied by the design of an aircooled single-cylindder internal combustion engine 1' according to the invention. Here the blower impeller 3 is attached to the side of the flywheel 2 facing the engine 1'. Between the engine 1' and the blower impeller 3 a mounting plate 12 preferably made from sheetmetal is provided and attached by means of bolts 13 to bosses l4 protruding from the crankcase 7 and from the cylinder head 9 in spaced relation to the engine and extends in transverse relation to the axis of the crankshaft 5. The mounting plate 12 presents a perforation 15 through which the extremity of the crankshaft carrying the flywheel blower 2, 3 extends. Another perforation 16 is provided in the upper portion of the mounting plate 12 adjacent to the cylinder 8.

Attached to the side of the mounting plate 12 facing away from the engine 1' is a cowl 4' encompassing the flywheel 2 with the housing 3 and forming at the same time the cooling-air spiral of the blower. This cowl 4 preferably is also made from sheet-metal. At the engine and a sheet-metal shell 17 is attached to the mounting plate 12 and encompasses the whole of the engine 1 including the crankcase 7. In a similar manner as the air-duct housing of the conventional internal combustion engine shown in FIGS. 1 and 2, the upper portion of this sheet-metal shell 17 forms in combination with the cylinder 8 and the cylinder head 9 a first cooling-air duct 1 1. This communicates via the perforation 16 of the mounting plate 12 with the interior of the cowl 4 and thus with the delivery end of the flywheel blower 2, 3.

The lower portion of the sheet-metal shell 17 encompasses the crankcase 7 in spaced relation thereto, accompanied by the formation of another cooling-air duct 18. The latter is separated from the firstmentioned cooling-air duct 11 by means of a partition 19 located above the upper boundary surface 20 of the crankcase 7 in spaced relation thereto and presenting a perforation adapted to the periphery of the cylinder 8. As a result, the space between the upper boundary surface 20 of the crankcase 7 and the partition 19 is also included in the cooling-air duct 18.

The cooling-air drawn in from the outside by means of the blower 3 is thus directed through the cooling-air duct 18 and the annular chamber 22 defined between the crankcase front wall 21 at the blower end and the mounting plate 12, and the aperture of the mounting plate 12 to the suction end of the blower 3. In the process, it sweeps over almost the whole of the external surfaces of the crankcase 7 in the cooling-air duct 18, and is therefore, instrumental in cooling the crankcase and consequently, the engine oil.

I claim:

1. An air-cooled single-cylinder internal combustion engine comprising, a crankcase having a crankshaft, a cylinder head mounted on the crankcase, a flywheel attached to one extremity of the crankshaft, a cooling-air blower located at a front end of the flywheel facing the engine and rigidly connected with the latter, a coolingair spiral surrounding the blower, a mounting plate extending in transverse relation to the crankshaft axis between the engine and the blower and attached to the engine, said mounting plate having a first perforation through which the crankshaft extends and which defines a cooling-air gap in combination with the crankshaft, and a second perforation located in the area of the cylinder and the cylinder head of the engine, a sheet-metal shell attached to the side of the mounting plate facing the engine and encompassing the engine, a partition arranged within said sheet-metal sheel and subdividing the free space between the engine and the sheet-metal shell into a lower and an upper portion, the lower portion defining a first cooling-air duct leading alongside the crankcase via the first perforation of the mounting plate to the suction end of the blower, the upper portion defining a second cooling-air duct leading from the second perforation of the mounting plate via the cylinder and cylinder head of the engine to the outside, a cowl attached to the side of the mounting plate facing the blower and covering the flywheel with the blower and cooling-air spiral, the space covered by the cowl interconnecting the two cooling-air ducts.

2. An internal combustion engine according to claim 1, wherein the mounting plate consists of sheet-metal.

3. An internal combustion engine according to claim 1, comprising bosses protruding from the side of the engine facing the blower, said mounting plate being attached to said bosses by means of bolts.

4. An internal combustion engine according to claim 1, having a perforation in said partition of the sheetmetal shell, the inner contours of said perforation being adapted to the periphery of the cylinder, said partition being located above an upper boundary surface of the crankcase and in spaced relation thereto and encompassing the cylinder. 

1. An air-cooled single-cylinder internal combustion engine comprising, a crankcase having a crankshaft, a cylinder head mounted on the crankcase, a flywheel attached to one extremity of the crankshaft, a cooling-air blower located at a front end of the flywheel facing the engine and rigidly connected with the latter, a cooling-air spiral surrounding the blower, a mounting plate extending in transverse relation to the crankshaft axis between the engine and the blower and attached to the engine, said mounting plate having a first perforation through which the crankshaft extends and which defines a cooling-air gap in combination with the crankshaft, and a second perforation located in the area of the cylinder and the cylinder head of the engine, a sheet-metal shell attached to the side of the mounting plate facing the engine and encompassing the engine, a partition arranged within said sheet-metal sheel and subdividing the free space between the engine and the sheet-metal shell into a lower and an upper portion, the lower portion defining a first coolingair duct leading alongside the crankcase via the first perforation of the mounting plate to the suction end of the blower, the upper portion defining a second cooling-air duct leading from the second perforation of the mounting plate via the cylinder and cylinder head of the engine to the outside, a cowl attached to the side of the mounting plate facing the blower and covering the flywheel with the blower and cooling-air spiral, the space covered by the cowl intErconnecting the two cooling-air ducts.
 2. An internal combustion engine according to claim 1, wherein the mounting plate consists of sheet-metal.
 3. An internal combustion engine according to claim 1, comprising bosses protruding from the side of the engine facing the blower, said mounting plate being attached to said bosses by means of bolts.
 4. An internal combustion engine according to claim 1, having a perforation in said partition of the sheet-metal shell, the inner contours of said perforation being adapted to the periphery of the cylinder, said partition being located above an upper boundary surface of the crankcase and in spaced relation thereto and encompassing the cylinder. 